雅思阅读精读：人类大脑与机器实验

　　Brain-computer interfaces sound like the stuff of science fiction. Andrew Palmer sorts the reality from the hype

　　脑机接口听起来像是科幻小说中的东西。在喧嚣的炒作中，安德鲁·帕尔默帮我们厘清现实状况

　　IN THE gleaming facilities of the Wyss Centre for Bio and Neuro engineering in Geneva, a lab technician takes a well plate out of an incubator. Each well contains a tiny piece of brain tissue derived from human stem cells and sitting on top of an array of electrodes. A screen displays what the electrodes are picking up: the characteristic peak-and-trough wave forms of firing neurons.

　　在日内瓦韦斯(Wyss)生物和神经工程中心那闪闪发光的大楼中，一名实验室技术人员从培养箱中取出一块多孔板。每个孔中都有小小一块来源于人类干细胞的脑组织放在一个电极阵列上。一块屏幕上显示着电极拾取的信息：神经元放电的特征峰谷波形。

　　To see these signals emanating from disembodied tissue is weird. The firing of a neuron is the basic building block of intelligence. Aggregated and combined, such “action potentials” retrieve every memory, guide every movement and marshal every thought. As you read this sentence, neurons are firing all over your brain: to make sense of the shapes of the letters on the page; to turn those shapes into phonemes and those phonemes into words; and to confer meaning on those words.

　　看到这些脱离身体的组织会发射信号让人感到有些怪异。神经元的放电是构建智力的基本材料。这些“动作电位”汇集和组合起来，就可拾取每一个记忆，支配每一个动作，组织每一个想法。在你读这句话的时候，你整个大脑中的神经元就在不停地放电：理解页面上的字母形状，把这些形状变成音素，把音素组成单词，再赋予这些单词意义。

　　This symphony of signals is bewilderingly complex. There are as many as 85bn neurons in an adult human brain, and a typical neuron has 10,000 connections to other such cells. The job of mapping these connections is still in its early stages. But as the brain gives up its secrets, remarkable possibilities have opened up: of decoding neural activity and using that code to control external devices.

　　这曲“信号交响乐”的复杂程度令人晕眩。成年人脑中有多达850亿个神经元，而一个典型的神经元细胞会连接到10000个同类细胞。描绘这些连接的工作还处于初期阶段。但是随着大脑秘密的逐步揭示，人们已经创造出非凡的可能性：解码神经活动并用这些密码控制外部设备。

　　A channel of communication of this sort requires a brain-computer interface (BCI). Such things are already in use. Since 2004, 13 paralysed people have been implanted with a system called Brain Gate, first developed at Brown University (a handful of others have been given a similar device). An array of small electrodes, called a Utah array, is implanted into the motor cortex, a strip of the brain that governs movement. These electrodes detect the neurons that fire when someone intends to move his hands and arms. These signals are sent through wires that poke out of the person’s skull to a decoder, where they are translated into a variety of outputs, from moving a cursor to controlling a limb.

　　要建立这样的沟通渠道，就需要一个脑机接口(BCI)。人们已经在使用这种东西了。自2004年以来，已有13位瘫痪者被植入了一个名为Brain Gate的系统，它是由布朗大学首先开发的(还有少数其他人也植入了类似的设备)。一组被称为犹他(Utah)阵列的小电极被植入到运动皮层，即大脑中管理运动的部分。如果有人想动动他的手和手臂，这些电极会检测到放电的神经元。信号通过穿出颅骨的电线传送到解码器，再转换成各种输出，如移动光标或控制肢体。

　　The system has allowed a woman paralysed by a stroke to use a robotic arm to take her first sip of coffee without help from a caregiver. It has also been used by a paralysed person to type at a rate of eight words a minute. It has even reanimated useless human limbs. In a study led by Bob Kirsch of Case Western Reserve University, published in the Lancetthis year, Brain Gate was deployed artificially to stimulate muscles in the arms of William Kochevar, who was paralysed in a cycling accident. As a result, he was able to feed himself for the first time in eight years.

　　该系统让一名中风瘫痪的妇女在没有看护者帮助的情况下用机器人手臂喝到了第一口咖啡。还有一位瘫痪者能以每分钟八个字的速度打字。它甚至让本已无用的肢体再次活动起来。由凯斯西储大学的鲍勃·基尔希(Bob Kirsch)领导的一项研究今年在《柳叶刀》上发表了论文，为在一次骑车事故中瘫痪的威廉·科切瓦(William Kochevar)人为部署了BrainGate，以刺激他手臂上的肌肉。结果八年来他第一次能够自己吃饭了。

　　Interactions between brains and machines have changed lives in other ways, too. The opening ceremony of the football World Cup in Brazil in 2014 featured a paraplegic man who used a mind-controlled robotic exoskeleton to kick a ball. A recent study by Ujwal Chaudhary of the University of Tübingen and four co-authors relied on a technique called functional near-infrared spectroscopy (fNIRS), which beams infrared light into the brain, to put yes/no questions to four locked-in patients who had been completely immobilized by Lou Gehrig’s disease; the patients’ mental responses showed up as identifiable patterns of blood oxygenation.

　　大脑和机器之间的互动还以其他方式改变了人们的生活。2014年，在巴西举行的世界杯足球赛开幕式上，一名截瘫男子用思维控制机器人外骨骼来踢球。在最近的一项研究中，图宾根大学的乌吉瓦·乔杜里(Ujwal Chaudhary)和四位合著者使用一种可将红外光束照进大脑的“近红外光谱”(fNIRS)技术，向四名因卢·贾里格症(Lou Gehrig's disease，又称肌萎缩性脊髓侧索硬化症、渐冻症)而完全失去行动能力的闭锁综合症患者提出是非问题，患者的思维反应表现为可辨认的血氧模式。

　　Neural activity can be stimulated as well as recorded. Cochlear implants convert sound into electrical signals and send them into the brain. Deep-brain stimulation uses electrical pulses, delivered via implanted electrodes, to help control Parkinson’s disease. The technique has also been used to treat other movement disorders and mental-health conditions. NeuroPace, a Silicon Valley firm, monitors brain activity for signs of imminent epileptic seizures and delivers electrical stimulation to stop them.

　　神经活动可以被刺激，也可以被记录。人工耳蜗将声音转换为电信号并将其送入大脑。深度脑刺激通过植入电极传送电脉冲来帮助控制帕金森病，该技术也被用于治疗其他运动障碍和精神疾病。硅谷的NeuroPace公司监测大脑活动来判断癫痫即将发作的迹象，并通过电刺激来阻止它们。

　　It is easy to see how brain-computer interfaces could be applied to other sensory inputs and outputs. Researchers at the University of California, Berkeley, have deconstructed electrical activity in the temporal lobe when someone is listening to conversation; these patterns can be used to predict what word someone has heard. The brain also produces similar signals when someone imagines hearing spoken words, which may open the door to a speech-processing device for people with conditions such as aphasia (the inability to understand or produce speech).

　　我们很容易想象出脑机接口可以如何应用于其他感官的输入和输出。加州大学伯克利分校的研究人员解析了聆听对话时大脑颞叶的电活动;这些模式可以用来推测听到的单词。当人们想象听到某些单词时，大脑也会产生类似的信号，这可能为患有失语症(无法理解或产生言语)的人开启语音处理设备的大门。

　　Researchers at the same university have used changes in blood oxygenation in the brain to reconstruct, fuzzily, film clips that people were watching. Now imagine a device that could work the other way, stimulating the visual cortex of blind people in order to project images into their mind’s eye.

　　这所大学的另一些研究人员利用大脑中的血氧变化来模糊地重建人们正在观看的电影片段。想想看，要是有一种设备能够反向工作，刺激盲人的视觉皮层，就可将图像投射到他们的头脑中。

　　If the possibilities of BCIs are enormous, however, so are the problems. The most advanced science is being conducted in animals. Tiny silicon probes called Neuropixels have been developed by researchers at the Howard Hughes Institute, the Allen Institute and University College London to monitor cellular-level activity in multiple brain regions in mice and rats. Scientists at the University of California, San Diego, have built a BCI that can predict from prior neural activity what song a zebra finch will sing. Researchers at the California Institute of Technology have worked out how cells in the visual cortex of macaque monkeys encoded 50 different aspects of a person’s face, from skin color to eye spacing. That enabled them to predict the appearance of faces that monkeys were shown from the brain signals they detected, with a spooky degree of accuracy. But conducting scientific research on human brains is harder, for regulatory reasons and because they are larger and more complex.

　　不过，如果BCI有巨大的可能性，那么问题也同样巨大。最前沿的科学研究正在动物身上进行。霍华德·休斯研究所、艾伦研究所和伦敦大学学院的研究人员开发出了一种称为神经像素(Neuropixel)的微小硅探针，用于监测小鼠和大鼠多个脑区中细胞层面的活动。加州大学圣地亚哥分校的科学家已经造出了一个BCI，可以从先前的神经活动中预测斑马雀将会唱什么歌。加州理工学院的研究人员已经揭示了猕猴视觉皮层中的细胞如何编码人脸从肤色到眼间距的50个不同特征。这使得他们能够根据检测到的大脑信号，以让人惊恐的准确度预测猴子看到的面部外观。但是由于监管方面的原因，加上人类大脑更大、更复杂，要在人脑上进行科学研究更为困难。

　　Even when BCI breakthroughs are made on humans in the lab, they are difficult to translate into clinical practice. Wired magazine first reported breathlessly on the then new Brain Gate system back in 2005. An early attempt to commercialize the technology, by a company called Cyberkinetics, foundered. It took NeuroPace 20 years to develop its technologies and negotiate regulatory approval, and it expects that only 500 people will have its electrodes implanted this year.

　　即使实验室中的人类BCI获得突破，它们也很难转化为临床实践。早在2005年，《连线》(Wired)杂志就首先兴奋地报道了当时新推出的BrainGate系统。一家名为Cyberkinetics的公司初步试图将这项技术商业化，却遭到惨败。NeuroPace花费了整整20年来开发技术并与监管审批部门谈判，它预计今年只有500人将植入它的电极。

　　Current BCI technologies often require experts to operate them. “It is not much use if you have to have someone with a masters in neural engineering standing next to the patient,” says Leigh Hochberg, a neurologist and professor at Brown University, who is one of the key figures behind BrainGate. Whenever wires pass through the skull and scalp, there is an infection risk. Implants also tend to move slightly within the brain, which can harm the cells it is recording from; and the brain’s immune response to foreign bodies can create scarring around electrodes, making them less effective.

　　目前的BCI技术通常需要专家来操作。BrainGate的关键人物之一，布朗大学的神经学家李·霍赫贝格(Leigh Hochberg)教授说：“如果你必须让一个神经工程学硕士站在患者旁边，那它的用处就不大了。”只要是电线穿过头骨和头皮的地方就有感染的风险。植入物也可能在脑内轻微移动，这可能会伤害它正在记录的细胞;大脑对异物的免疫反应会在电极周围产生瘢痕，让它们的效果变差。

　　Moreover, existing implants record only a tiny selection of the brain’s signals. The Utah arrays used by the BrainGate consortium, for example, might pick up the firing of just a couple of hundred neurons out of that 85bn total. In a paper published in 2011, Ian Stevenson and Konrad Kording of Northwestern University showed that the number of simultaneously recorded neurons had doubled every seven years since the 1950s (see chart). This falls far short of Moore’s law, which has seen computing power double every two years.

　　而且，现有的植入物只记录了大脑信号中很小的一部分。例如，BrainGate财团使用的犹他阵列也许仅仅拾取了几百个神经元放电的信号，而神经元总计有850亿个。在2011年发表的一篇论文中，西北大学的伊恩·史蒂文森(Ian Stevenson)和康拉德·科尔丁(Konrad Kording)提出，自20世纪50年代以来，能一次被同时记录的神经元数量每七年翻一番(见图表)。这与摩尔定律也就是计算能力每两年翻一番相差甚远。

　　雅思阅读高频词汇

　　symphony 交响乐团

　　regulatory 监管

　　Neuro engineering 神经工程

　　interfaces 接口

　　infection 感染

　　deploy 部署

　　cortex 皮质

　　array 数组